CGRO, one of NASA’s gamma-ray observatories, didn’t resemble any normal telescope. For one thing, it didn’t have a mirror. Instead of collecting light, it tracked rare, difficult-to-detect gamma radiation. Its four instruments observed gamma rays indirectly by monitoring the flashes of visible light, called scintillations, that occurred when the gamma rays struck the liquid crystal detectors built into the instruments. Each instrument was designed to study a different portion of the gamma-ray spectrum. Solar panels and batteries provided the telescope with power.
Live long and prosper
Get to the root of it
CGRO, the second telescope in NASA’s Great Observatories program, was only supposed to live for 2 to 5 years, but it outlasted all the estimates. In December of 1999 one of its gyroscopes failed. Gyroscopes are devices that help position space telescopes.
NASA was worried that if a second gyroscope failed, the telescope would become hard to control. Though the telescope was still functional, NASA decided to bring it out of orbit while it could still direct the satellite’s dive into the atmosphere over an unpopulated area. The telescope broke apart and burned up above the Pacific Ocean in 2000. But it left behind a legacy — the telescope helped astronomers establish that huge, sudden blasts of energy, called “gamma-ray bursts,” were coming from outside our galaxy.
